The invention relates to a spot welding cap changer with a cap extractor and two cap magazines, the cap extractor having a gripper with spring-loaded, pivoting jaws, which in response to a turning and axial extraction movement detaches a spot welding cap of a pincer spot welding head inserted into it from a shaft of the pincer welding head in such a way that it is clamped to prevent twisting, and the cap magazines holding spot-welding caps in a cap carrier in such a way that they are circularly arranged in a directed and oriented manner and are one by one transported by an advancing force against a stop, into an access position allowing to attach them axially to the free shaft of the pincer and to extract them with it.
Such a mechanical electrode cap changer is known from the DE 102 22 248 A1. It has a two-part cap extractor, accessible from both sides, in a body separate from the magazine.
Since gravity causes the caps to slide against a cap stop, the device can only be operated stationary in the vicinity of a mobile welding robot. Changing caps at a stationary pincer spot welding head, to which each component is fed by a robot for welding, is therefore not possible. The pincer spot welding heads/welding installations often have short shafts, which are for instance curved, so that the cap extractor, equipped with three large jaws and accordingly big, cannot be positioned for extraction.
It is the object of the invention to provide for an automatic faster and safer exchange of the spot welding caps both at mobile and stationary spot welding installations with a short access distance.
The solution resides in that the cap extractor has two opposed grippers, each with jaws that are open at their ends and can be rotated towards each other with approximately parallel toothed grip surfaces whose distance is slightly smaller than a diameter of a spot welding cap, and each cap magazine contains a cap carrier, which, driven by a spring box, presses by way of its advancing force one of the caps respectively against the stop, and in the access position a rim overlap overlaps the cap on one side.
Advantageous forms of the invention are indicated in the subclaims.
In the new embodiment the cap extractor and the magazine are mounted on a support which preferably is spring-mounted. In contrast to the known system, the new construction design gives the possibility not only to be used at welding robots, but also at stationary pincer welding heads or welding installations.
Compared with the known clamping system with three jaws, the new cap-extraction installation provides for shorter clamp and spin travels, therefore much shorter intervals for detaching the caps. Moreover, from the smaller design results a wider array of application, for instance at non-standard pincers or very short, curved shafts.
The two cap extractors are each open at the ends of the jaws and thus accessible to a cap. The jaws grip it directly by way of the undersize of their distance and detach the cap, whereby a rotation around an angle of about 30-60° suffices. This way a cap change is possible even in extremely narrow confines. Since the two grippers are oriented in opposite directions, respectively one of them is accessible from the various sides in a clockwise rotation, so that no turning of the pincer is necessary, even if the pincer shafts are screwed on.
Furthermore, the round magazine is much more compact than the straight magazine functioning by gravity of the known installation. It can be held and operated in any position because of the spring drive.
Furthermore, the two round magazines arranged on parallel axes provide in each case for an access with short radial travel to the access positions in the access openings. In an embodiment with a magazine cover, this cover is directly shifted during access, far enough to let the rim overlap uncover the cap frame, so that the detaching is possible. The example shows a radial infeed and an axial access of the shafts into the magazine.
Both partial devices, the cap changer, and the cap magazine, are mounted on a support close to one another, and thus can be set up stationary, or mounted to a robot arm in a fixed or detachable manner. In the first case the welding robot changes the caps of its own pincer, and in the second case the robot changes the caps at the stationary pincers or installations respectively by means of the device. The changing device at the robot arm is movably mounted, constantly ready for operation in a free space next to the gripper of the robot or on a guide rail, or it is located in a parking position, where it can be picked up and brought to operation by the gripper; this is called alternating pincer principle.
Advantageously, cap sensors are arranged on the device., which indicate whether a cap is in place or not. Moreover, the charging level of the magazines is monitored. This way it is ensured that after a cap change a cap is in place at the shaft of the pincer welding head before the cooling water is switched on. Furthermore it can be verified, whether the old cap was removed, when it is reported that there is no cap in place while the shaft is approaching.
The embodiment of the cap magazine without a cover holds the welding caps in an elastic cap carrier in a close fit, axially movable by propulsive or tractive force.
Advantageous embodiments are represented in the
Offset to the rear from the cap extractor 2 respectively one cap magazine 3, 3A laterally offset to the other is mounted on the mounting plate 50, with the magazine cover 4 respectively directed laterally and the access openings 40 oriented axially parallel to the extracted welding caps K that are still held by the gripper, so that the shafts of the pincer spot welding head have to travel only short distances while changing the caps.
The initial pressing force of the jaws 21, 22 is caused by a bracing spring 26, which for example, is formed as a spiral or bracing spring with spread ends, each pressing against a jaw arm 25.
On the infeed side the grippers 20 are provided with infeed skews 27, 28. From these extend the roughly parallel grip surfaces 23, each with a toothing in opposite direction 29A, 29B, as
The cover 4 has a small rim overlap 41 of the cap frame in the curve of the access opening 40, an induct skew 42 connecting to said rim overlap which is cascaded to the top side of the cover. At an embodiment with a hinged cover 4, a slot 43 is formed, through which reaches a bracket 34, bevelled on the outside, which keeps the cover 30 shut.
On the other side of the access opening 40 a hinge 44 with a slotted hole 45 is formed in the extension level of the cover, the cones 46 of said hinge being held in a hinge support 47.
The plate-shape bracket 34 extends in a diagonal guiding slot on the cover of the spring box 33. In the closed state, as shown here, a compression spring arrangement 35, held in the cover, extends from the bracket 34 and is supported by means of a support pin 36 on the rounded hinge support 47, and presses the bracket 34 in the closed position, in which it overlaps the cover 4 in the closed state and holds the rim overlap 41 in the overlap position, the cone 46 being in the rear stop position in the slotted hole 45, as
The compact construction of the cap extractor with the magazines allows for a significant reduction of the changing times, for example, from 22 to 17 sec, which corresponds to about 23%.
1 spot welding cap changer
2 cap extractor
20 gripper
21, 22 jaws
23 grip surfaces
24 pivot joint
25 jaw arm
26 bracing spring
27, 28 infeed skews
29A, 29B toothing
3, 3A cap magazine
30 drill holes
31 cap carriers
32 stop
33 spring box
34 bracket
35 compression spring
36 support pin
4 magazine cover
40 access opening
41 rim overlap
42 induct skew on the cover
43 slot in the cover
44 hinge
45 slotted hole in the hinge
46 cones
47 hinge support
48 cover rim
49 compression spring chamber
5 support rail
50 mounting plates
60, 61 cover plates
62 jaw plate
A gripping jaw distance
D outside diameter of the caps
K cap
P advancing force
M1, M2 semicircle, centres
Number | Date | Country | Kind |
---|---|---|---|
102005035915.9 | Jul 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2006/064417 | 7/19/2006 | WO | 00 | 7/30/2008 |